Bladed discs, or blisks, are conventionally manufactured by machining the aerofoil and disc elements from a single forging. This is often the most appropriate manufacturing technique where the aerofoils are relatively small but for discs having larger aerofoils, this machining technique wastes a lot of material.
Flash producing welding processes are processes in which material that is softened by heat generated by friction, pressure or an external heat source, is expelled from the weld joint zone.
The use of linear friction welding (LFW) to manufacture bladed discs for use in gas turbine engines offers much better material utilisation, with post-weld machining being required only in regions adjacent to the weld and below the disc rim.
One problem with flash producing welding processes in general, and with LFW manufacturing techniques in particular, is that flash is expelled sideways from the weld joint. In the case of bladed discs, this flash is problematic because the flash generated by one joint between aerofoil and rotor can be expelled sufficiently far from the joint as to interfere with the adjacent joint. This means that either de-flashing is required after each weld, or only alternate aerofoil to rotor friction welds may be completed before the flash is removed. The part-finished blisk must then be refitted to the LFW apparatus to have the intervening aerofoil to rotor friction welds completed.
De-flashing after each weld increases the cost and time required to finish the component. replacing the part-finished blisk in the linear friction welding apparatus in order to have the remaining linear friction welds completed requires careful and precise repositioning the part-finished component, which further increases the cost and time required to finish the component.